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Snake eels of the genus Ophichthus (Anguilliformes: Ophichthidae) from Myanmar (Indian Ocean) with the description of two new species
Abstract
Two new species of ophichthid eels, subfamily Ophichthinae, are described and illustrated from specimens collected from Myanmar by the R/V Dr. Fridtjof Nansen. Included are: Ophichthus nansen sp. nov., from 103–106 m depth, which is unique in its vertebral number (11-53-116), dorsal-fin origin (above mid-pectoral fin), jaw dentition (small, conical and mostly biserial), and coloration (dark gray-brown, fins black); and Ophichthus naga sp. nov., from 455–459 m depth, which is unique in its vertebral number (15-65-153), dorsal-fin origin (well behind pectoral fin), dentition (small, conical, biserial in upper jaw and uniserial in lower jaw and on vomer), and dark brown coloration. Also new to Myanmar are Ophichthus cephalozona Bleeker, 1864, and O. lithinus (Jordan & Richardson, 1908), which are diagnosed and treated herein.
... The snake eel genus Ophichthus comprises more than 80 species and is the most speciose among all genera in the family Ophichthidae. The genus is a polyphyletic assemblage and many new species were added in the recent decade (McCosker, 2010;McCosker et al., 2012;McCosker & Ho, 2015;McCosker & Psomadakis, 2018;Hibino et al., 2019a, b). ...
... The species of Ophichthus can be primarily separated by the posterior nostril being situated above upper lip with a large flap covering it, or within upper lip without a flap; dorsal-fin origin (DFO) before pectoral-fin base, above pectoral fin or not far behind tip of fin, or more than one pectoral-fin length behind tip of the fin. Among the species with DFO more than one pectoral-fin length behind tip of the fin, they can be further separated by base of anal fin pale to tail tip, or blackened approximately one head length in advance of tail tip (McCosker, 2010;McCosker & Ho, 2015;McCosker & Psomadakis, 2018;Hibino et al., 2019a, b). ...
... The new species has a far posterior DFO which is distinct from all of its congeners. Among these congeners, the new species is most similar to Ophichthus humanni McCosker, 2010, Ophichthus kusanagi Tashiro, 2019b, andOphichthus naga McCosker &Psomadakis, 2018, but can be separated by different body proportions and vertebral formula. ...
A new snake eel, Ophichthus longicorpus, is described from 13 specimens from Lương Sơn, Nha Trang, Vietnam. It is distinguished by having dorsal-fin origin situated at 4.4-6.7 pectoral-fin length behind head; anus situated at about middle of total length; trunk very long, 4.1-4.9 head length; head length 10.5-12.2 in TL; posterior nostril above upper lip, covered by a large flap extending well below the edge of mouth gape; pectoral fin small, pointed posteriorly; no barbel on upper lip; cephalic sensory pores: SO 1 + 4, POM 6 + 2; teeth moderately large and conical, biserial anteriorly and uniserial posteriorly on both jaws and vomer; body colour yellowish-brown dorsally and grayish-brown ventrally; dorsal fin light grayish with indistinct white margin; anal fin white with slightly grayish base; and total vertebrae 156-164, mean vertebral formula 27-68-159. Specimens of Echelus polyspondylus McCosker & Ho are newly reported from Vietnam.
... Because of less distinguishable morphological features and various shapes of body in different growth stages, it brings great difficulties to effective species identification and phylogeny analysis of this group. The studies on ophichthid eels are limited to morphological identification and new species description [3][4][5][6][7][8]. There have been no reports on the genome of snake eels until now. ...
Ophichthidae fishes limit to continental shelf of all tropical and subtropical oceans, and contain more than 350 species, representing the greatest specialization diversity in the order Anguiliformes. In this study, we conducted a genome survey sequencing (GSS) analysis of Ophichthus evermanni by Illumina sequencing platform to briefly reveal its genomic characteristics and phylogenetic relationship. The first de novo assembled 1.97 Gb draft genome of O. evermanni was predicted based on K-mer analysis without obvious nucleotide bias. The heterozygosity ratio was 0.70%, and the sequence repeat ratio was calculated to be 43.30%. A total of 9,016 putative coding genes were successfully predicted, in which 3,587 unigenes were identified by gene ontology (GO) analysis and 4,375 unigenes were classified into cluster of orthologous groups for enkaryotic complete genomes (KOG) functional categories. About 2,812,813 microsatellite motifs including mono-, di-, tri-, tetra-, penta-, and hexanucleotide motifs were identified, with an occurrence frequency of 23.32%. The most abundant type was dinucleotide repeat motifs, accounting for 49.19% of the total repeat types. The mitochondrial genome, as a byproduct of GSS, was assembled to investigate the evolutionary relationships between O. evermanni and its relatives. Bayesian inference (BI) phylogenetic tree inferring from concatenated 12 protein-coding genes (PCGs) showed complicated relationships among Ophichthidae species, indicating a polyphyletic origin of the family. The results would achieve more thorough genetic information of snake eels and provide a theoretical basis and reference for further genome-wide analysis of O. evermanni.
... However, Ophichthus First record of Marbled snake eel, Ophichthus lithinus (Jordan & Richardson 1908) lithinus is distinguished from other similar species such as Brachysomophis cirrocheilos (Bleeker, 1857) in having lower jaw shorter than upper jaw vs. jaws are almost equal in size; cirri present in both the lips vs. cirri absent in lips. The species also distinguished from its closely related species Ophichthus cephalozona (Bleeker, 1864) by having a smaller body depth of 24-30 in TL vs. larger body depth more than 35 in TL (Table 1) Ophichthus lithinus is known to occurs from the Indo-Pacific to the Western Pacific waters through Australia, Philippines, Republic of Korea (Kim et al., 2005), Taiwan (Hoese et al., 2006), Southern Japan (Masuda et al., 1984) Papua New Guinea (Kailola, 1987), Hong Kong (South China Sea) (Ni & Kwok, 1999), Vietnam (Nguyen & Nguyen, 1994), Myanmar (Ayeyarwady Delta) (McCosker & Psomadakis, 2018), India (Digha Coast and Tamil Nadu) (Ray et al., 2015). ...
The present paper reports the first record of marbled snake eel, Ophichthus lithinus (Jordan & Richardson 1908) from Bangladesh marine water. The authors confirmed the identification of the species by the morphological characteristics of a single individual collected during the field survey conducted from November 2019 to March 2020 in Saint Martin’s Island, Bangladesh. This paper also confirms the first occurrence of the genus Ophichthus Ahl 1789 in the country.
... nov.), a longer tail (about 2 in TL vs. 2.15 in TL) and a shorter head (11.5-12.0 in TL vs. 9.6-11.1 in TL). The new species is similar genetically and also in its morphometry and meristics to Ophichthus lithinus (Jordan & Richardson 1908), a medium-sized (to 148 cm TL) shallow sand and mud bottom species known from Taiwan, the Philippines, northern Australia, India, and Myanmar (Ray et al. 2015;McCosker & Psomadakis 2018). This species has an elongate, cylindrical, tapering and laterally compressed body, a pointed snout and tail tip; a body depth behind gill openings of 32-37 in TL; its anus is at midbody; its head length is 9.7-11.7 in TL; it has uniserial dentition; a third preopercular pore; a notable barbel along the upper lip; and a similar pectoral-fin shape. ...
A new species of snake eel Ophichthus olivaceus is described based on two specimens trawled from a depth of 35–63 m from a soft substratum off Jizan, Red Sea coast of southern Saudi Arabia. It differs from its congeners by the following combination of characters: vertebrae 141–145; tail moderately short (2.15 in TL); head short (9.6–11.1 in TL); uniserial teeth in jaws and on vomer; pectoral fins slightly elongate, not lanceolate, upper rays longer than the lower; dorsal-fin origin above middle of pectoral fin; and a generally uniform, dark tan body with an olivaceous hue shading to tan or pale orange ventrally, with two pale yellow blotches above pectoral-fin base, snout and lower jaw dark brown, and olivaceous median fins. Its divergence from other mitochondrial-analyzed species is shown by phylogenetic analysis of the mitochondrial COI barcoding region. A key to the Indian Ocean species is provided.
... Currently 345 valid species are recognized, Myrophinae (69) and Ophichthinae (276) (Fricke et al. 2019). Most inhabit depths of less than 200 m, but recent deep-sea explorations have uncovered many new species living at depths of more than 200 m (McCosker et al. 1989;McCosker 1999;McCosker & Chen 2000;McCosker 2010;McCosker & Ho 2015;Tashiro et al. 2015;McCosker & Psomadakis 2018;Hibino et al. 2019). They are rarely encountered in sampling because of their specialized burrowing nature. ...
A deep-sea species of snake eel (family Ophichthidae, subfamily Ophichthinae) Ophichthus mccoskeri sp. nov. is described based on 6 specimens (331-447 mm total length) trawled at 314-363 m depth in Andaman waters, India. This species is differentiated from its deep-water congeners by a combination of characters such as its large eyes, dorsal-fin origin a short distance behind pectoral-fin tip, anal fin black posteriorly, three preopercular pores, maxillary and mandibular teeth ending as triserial, and in a vertebral formula of 20/55/153.
Biodiversity surveys are crucial to monitor the health of threatened aquatic ecosystems, such as tropical estuaries and mangroves. Conventional monitoring methods are intrusive, time-consuming, substantially expensive and frequently only provide rough assessments in complex habitats. Recent advanced molecular methods such as environmental DNA (eDNA) using high-throughput sequencing technology are promising although only few applications in tropical estuarine ecosystems have been reported. In this study, we explore the advantages and limitations of an eDNA metabarcoding survey on the fish community of the Merbok Estuary (Peninsular Malaysia). COI and 12S eDNA metabarcoding assays collectively detected 178 species belonging to 127 genera, 68 families, and 25 orders. This approach captured significantly more species than in any previous traditional surveys, including a few species of conservation importance. However, we highlight three limitations: (1) in the absence of a comprehensive reference database the identities of several species are unresolved; (2) a fraction of previously documented specimen-based diversity was not captured by the current method, may be as a consequence of PCR primer specificity, and (3) the detection of non-resident species; stenohaline freshwater taxa (e.g. cyprinids, channids, osphronemids) and marine coral reef taxa (e.g. some sharks, holocentrids and syngnathids), not known to frequent estuaries, leading to the supposition that their DNA have drifted into the estuary through water movement. The community analysis revealed that fish diversity along the estuary is not homogenous, with the upstream more diverse than further downstream. This may be the consequence of the salinity or pollution gradients. In summary, we demonstrated the practicality of eDNA metabarcoding in assessing fish community and structure within a complex and rich tropical environment within a short sampling period. However, some limitations need to be considered and addressed to fully exploit the efficacy of this approach, in particular the development of a comprehensive reference genetic database.
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